In recent years, as electrophotographic photosensitive members used in electrophotographic apparatuses, electrophotographic photosensitive members (organic electrophotographic photosensitive members) having an undercoat layer which contains a metal oxide particle and a photosensitive layer which contains a charge-generating substance and a charge-transporting substance and which is formed on the undercoat layer have been used.
With recent enhancement of image quality and increases in the processing speed of electrophotographic apparatuses, one of the problems to be solved is to suppress variations in potential, i.e., changes in dark-area potential (charge potential) and the like, in electrophotographic photosensitive members when repeatedly used.
As a technique for suppressing variations in potential, there has been disclosed in PTL 1 a technique in which an undercoat layer of an electrophotographic photosensitive member is incorporated with a metal oxide particle to which an acceptor compound (organic compound) is added.